#include <iostream>
#include <assert.h>
#include <stdlib.h>
using namespace std;
int len;
char * tran(long long a)
{
  char *string=(char *)calloc(100,sizeof(char));
  assert(string!=NULL);
  int sub=a/26;
  int mod=a%26; 
  len=sub/26+(sub%26?1:0)+(mod>0);
  int i;  
  if(mod>0)	string[len-1]=mod+'A'-1;
  for(i=0;i<sub/26;i++) string[i]='Z';
  if(sub%26>0) string[i]=sub%26+'A'-1;
  return string;
}
int main()
{
  long long a;
  cin>>a;
  cout<<tran(a)<<endl;
  return 0;
}